Substrate processing often involves exposing a substrate wafer to radiation. For example, a substrate may be exposed to ultraviolet (UV) light, including high power UV radiation. Substrates may be exposed to high power light (e.g., UV light), for example during a photolithography process and/or other manufacturing processes. Exposing an entire substrate to a substantially uniform intensity light source may ensure that the entire substrate is treated similarly at all locations, for example to ensure consistency in a photolithography operation across the entire substrate. However, broadband and/or narrower band high power UV flood source options or any exposure source may have significant dose non-uniformity across an exposed area and through time. High power UV flood exposure source or other source design and/or selection may be subject to several considerations in semiconductor processing. For example, considerations may include the following:
1. Throughput: a combination of power and exposure method (e.g., whole wafer, rastering spot, etc.)
2. Intensity versus wavelength (e.g., when process absorbance is over a narrow wavelength range)
3. Dose uniformity from source in exposed area (e.g., non-uniformity can be >5% and sometimes >10% in some systems)
4. Dose control through time
5. Cost trade-offs for throughput and uniformity considerations.
Many low cost, high power UV flood options suffer from significant dose non-uniformity across the exposed area (e.g., non-uniformity can be >5% and sometimes >10%). Many of the same low cost, high power UV flood options also suffer from drifting average power through time.
Some high power UV source examples are shown in table 100 of FIG. 1. In some sources, a microwave powered UV lamp, such as those provided by Nordson, or an LED array may be used, for example. The microwave power lamp source may use 6″ or 10″ bulbs that create a light bar of some desired intensity. However, the light bar may have significant intensity fall-off FIG. 2 is a sample UV intensity map 200. As shown in this example map 200, intensity may be greatest near the center of the UV lamp and may fall off towards the lamp edges. This map 200 is one example, but UV sources may have different intensity distributions based on variables such as source type, source age, presence of manufacturing defects, etc.
At times, it may be desirable to achieve a non-uniform predetermined exposure.